Fixing hidden dependencies.

Header files base/videosinkinterface.h and base/videosourceinterface.h
were not part of any target (because they cause 2 dependency cycles).

This CL uncomment them so GN can keep dependencies under control, the
2 dependency cycles will be removed as part of webrtc:6828.

Bug: webrtc:6828
Change-Id: I5c5580facc010ba619e105a9b8a572ac70169a01
Reviewed-on: https://webrtc-review.googlesource.com/27621
Reviewed-by: Patrik Höglund <phoglund@webrtc.org>
Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#20970}
diff --git a/modules/video_capture/BUILD.gn b/modules/video_capture/BUILD.gn
index 31a4b65..9a44967 100644
--- a/modules/video_capture/BUILD.gn
+++ b/modules/video_capture/BUILD.gn
@@ -30,6 +30,7 @@
     "../..:webrtc_common",
     "../../api:video_frame_api_i420",
     "../../common_video",
+    "../../media:rtc_media_base",
     "../../rtc_base:rtc_base_approved",
     "../../system_wrappers",
   ]